The present invention is directed to heat exchanger cleaning devices. Since the invention of the heat exchanger, they have been plagued by contamination problems that require the unit to be cleaned. Some designs allow disassembly for manual cleaning, while others are sealed. Many critical processes (food, dairy, pharmaceutical, petroleum, paint, etc.) require that the system be sealed and that all components in the system be designed for “clean-in-place” to prevent or minimize contamination. Still, there are times when the design of heat exchangers must balance between size and configuration of exposed material contact surfaces (to optimize thermal transfer area) and cleanability. Most manufacturers recommend that heat exchange units be cleaned thoroughly and regularly to prevent fouling and system contamination. The ability to clean the unit without disassembly minimizes disturbance to gaskets and seals that can result in leakage and reduces the chance for system contamination.
Many systems have been designed to clean heat exchangers, both off line (after the heat exchanger is removed from the host system), or in place. Some are comprised of a tank from which a cleaning solution is pumped through the heat exchanger to “flush out” any impurities. Often these are used to “back flush” the unit, where the connection of the circulation system causes the flow of the cleaning solution to be opposite that of the normal fluid flow through the heat exchanger. Back flush operations can require repiping to achieve the altered flow directions. The flushing fluid may be an aqueous material, organic solvent-based systems, or fluid that combines the two.
Still another commercially available solution is to use a mixture of solvent and air to create turbulence in the heat exchangers typically in the standard flow direction. While this does create turbulence and a “scrubbing effect,” the mixture of air and solvent is less dense than the cleaning solution alone and therefore has less force behind it. These systems may be piped to “back flush” the unit, but manual repiping is required to change the direction of flow, and this can be a slow and laborious process that does not create the immediate disturbance necessary to dislodge trapped particles. Yet another disadvantage of this type of system is that, if a volatile solvent is used, the mixture of air and solvent comprises two of the three legs of the fire triangle and only an ignition source (in many cases, just a spark) is necessary to create catastrophe.